A large variety of enzymes are important in medicine, industry, and other applications. Discovery of novel enzymes has gone hand-in-hand with development of certain industries, for example the discovery of bacterial restriction enzymes and the development of genetic engineering. Enzymes are important in various medical pathologies (Fang J., et al., Proc. Natl. Acad. Sci. U.S. 97: 3884–3889, 2000), as novel therapeutics (U.S. Pat. No. 6,210,667 issued Apr. 3, 2001), as targets for development of novel therapeutic agents, for example, HIV protease (U.S. Pat. No. 6,271,235 issued Aug. 7, 2001), in industrial processes such as antibiotic biosynthesis (U.S. Pat. No. 6,258,555 issued Jul. 10, 2001), degradation of unwanted materials such as polyurethane (U.S. Pat. No. 6,180,381, issued Jan. 30, 2001) and in the food industry (U.S. Pat. No. 5,827,712, issued Oct. 27, 1998). The need to obtain novel enzyme activities is so great that protein engineering research has been directed toward development of catalytic antibodies (U.S. Pat. No. 5,807,688, issued Sep. 15, 1998).
Thin bimorph microcantilevers can undergo bending (deflection) due to differential stresses following exposure to and binding of a compound from their environment, for example in a fluid sample. Soft microcantilevers having spring constants less than 0.1 N/m are sensitive to stress differentials that arise as a result of interactions between extremely small amounts of a substrate material on a surface of the microcantilever and one or more materials in a sample. For a given microcantilever with a specially designed coating layer, the deflection yields information about components of the environment to which the microcantilever is exposed. Microcantilevers are capable of detecting calorimetric enzyme-mediated catalytic biological reactions with femtoJoule resolution. (Thundat et al., “Microcantilever Sensors”, Microscale Thermophysical Engr. 1, pgs. 185–199, 1997.) Oligonucleotide interactions within a sample can be detected using a monolithic array of test sites formed on a surface to which the sample is applied (U.S. Pat. No. 5,653,939).
There is a need for methods and an apparatus for detecting an interaction between an enzyme and its enzymatic substrate, for detecting a protein having an enzymatic activity or a related molecule, such as a catalytic antibody, or a binding or associating protein, as measured by a response of a microcantilever to a stress caused by changes in free surface energy and bonding energy. There is a need in medical and veterinary diagnostics, and in research, for detection and analysis of binding and activities of enzymes and enzyme-like proteins.